This application is based on the assumption that the individual's habitual pattern of response to environmental stress is a significant component in the genesis of essential hypertension. In keeping with this assumption, we propose to employ certain biofeedback and behavioral conditioning techniques in examining whether the hypertensive's response to stress can be modified. Generally, our techniques are designed to teach subjects to lower arousal level (through profound muscle relaxation and allied techniques) and to employ this ability in moderating one's response to everyday stress situations. Several independent sources have reported that systematic training in muscle relaxation and its regular application in everyday life, are useful in moderating essential hypertension. We think it is therefore important: (1) To determine whether the previously reported positive findings can be confirmed. (2) To see whether the effects can be strengthened by the addition of several newer biofeedback techniques. (3) To attempt to identify, and be able to predict, the types of hypertensives likely to respond favorably to this kind of treatment. Our main study will determine whether a combination of EMG feedback and skin temperature feedback training will reduce blood pressure in selected hypertensives. Patients will be studied for evidence both of lowered blood pressure and diminished peripheral resistance (using a non-invasive plethysmorgraphy technique). Pressures in hypertensives at sleep-onset will also be assessed to test the hypothesis that patients whose pressures drop most at sleep-onset are those most responsive to EMG feedback and/or skin temperature feedback training. A final study will examine whether the conditioning of an autonomic response occurs more readily if it is first preceded by systematic training in muscular relaxation.